1. Field of the Invention
The present invention relates to a biodegradable aliphatic polyester elastomer. The biodegradable elastomer of the invention is prepared by crosslinking aliphatic polyester containing aliphatic unsaturated polybasic acid as a polymer constituting ingredient.
The biodegradable elastomer of the invention can provide formed articles and workpieces by utilizing the favorable properties of the elastomer.
2. Related Art of the Invention
As well known in the art, there are several processes for preparing a high molecular weight aliphatic polyester having a weight average molecular weight of 15,000 or more from aliphatic polyhydric alcohol and aliphatic polybasic acid.
U.S. Pat. No. 5,401,796 has disclosed a process for preparing aliphatic polyester having a weight average molecular weight of 15,000 or more, comprising conducting a heat dehydration reaction of aliphatic polyhydric alcohol or a mixture thereof with aliphatic polybasic acid or a mixture thereof, or an oligomer of these ingredients in a reaction mixture containing an organic solvent.
According to the process, high molecular weight aliphatic polyester thus obtained contains no impurity, is in a low grade of coloration, and has strength which is sufficient for formed items such as films and filaments.
However, the patent has disclosed aliphatic saturated polyester alone and no disclosure has been found at all on aliphatic unsaturated polyester or a biodegradable elastomer which differs in chemical properties.
U.S. Pat. No. 4,888,413 has disclosed a poly(propylene glycol fumarate) composition having a weight average molecular weight of 500-3,000.
The object of the art is to provide a composition which is specified in a terminal group ratio, weight average molecular weight and number average molecular weight, has improved mechanical properties and biodegradability, has high reproducibility, and is useful for biomedical applications such as bone cement.
Further, Japanese Laid-Open Patent Hei 7-133333 has disclosed a preparation process of biodegradable high molecular weight aliphatic polyester, comprising mixing aliphatic unsaturated polyester having a weight average molecular weight of 30,000 or more with polyester comprising 1 equivalent or more of polymerizable unsaturated group for 100 equivalents of terminal group and conducting copolymerization of unsaturated bonds in the mixture in the presence of organic peroxide.
According to the process, a biodegradable high molecular weight aliphatic polyester thus obtained has sufficient physical properties for preparing various formed items, can steadily increase the weight average molecular weight as compared with the number average molecular weight and can restrict scattering of viscosity.
However, these prior arts have no disclosure at all on the biodegradable elastomer.